[stgt] [PATCH] SBC READ6/10/12/16: Add handling of residual overflow/underflow.

[Alexander Nezhinsky]

sorry for resending, sent HTML for the first time...

On Sat, Mar 23, 2013 at 11:16 PM, Ronnie Sahlberg
<ronniesahlberg at gmail.com> wrote:
>
> This patch adds support to return overflow/underflow residuals
> for the cases where the transport layer (iSCSI, ...) specifies
> an EDTL that is not matching the SCSI transdfer length.
>
> Additionally, in case of residual underflow it will also clamp the size of
> returned DATA-IN to the amount of data that was actually read and not the
> EDTL that was requested.
>

>
> diff --git a/usr/sbc.c b/usr/sbc.c
>
> index 48dab04..26cceb1 100644
> --- a/usr/sbc.c
> +++ b/usr/sbc.c
> @@ -226,6 +226,8 @@ static int sbc_rw(int host_no, struct scsi_cmd *cmd)
>         int ret;
>         uint64_t lba;
>         uint32_t tl;
> +       long residual = 0;
> +       long length;
>         unsigned char key = ILLEGAL_REQUEST;
>         uint16_t asc = ASC_LUN_NOT_SUPPORTED;
>         struct scsi_lu *lu = cmd->dev;
> @@ -335,12 +337,36 @@ static int sbc_rw(int host_no, struct scsi_cmd *cmd)
>         cmd->offset = lba << cmd->dev->blk_shift;
>         cmd->tl     = tl  << cmd->dev->blk_shift;
>
> +       /* Handle residuals */
> +       switch (cmd->scb[0]) {
> +       case READ_6:
> +       case READ_10:
> +       case READ_12:
> +       case READ_16:
> +               length = scsi_get_in_length(cmd);
> +               if (length != cmd->tl) {
> +                       residual = length - cmd->tl;
> +
> +                       if (length > cmd->tl) {
> +                               length = cmd->tl;
> +                               scsi_set_in_transfer_len(cmd, cmd->tl);
> +                               scsi_set_in_length(cmd, cmd->tl);
> +                       }
> +               }
> +               break;
> +       }
> +
>         ret = cmd->dev->bst->bs_cmd_submit(cmd);
>         if (ret) {
>                 key = HARDWARE_ERROR;
>                 asc = ASC_INTERNAL_TGT_FAILURE;
> -       } else
> -               return SAM_STAT_GOOD;
> +               goto sense;
> +       }
> +
> +       if (residual)
> +               scsi_set_in_resid(cmd, residual);
> +
> +       return SAM_STAT_GOOD;
>
>  sense:
>         cmd->offset = 0;
> --
> 1.7.3.1
>

I think that scsi_set_in_resid_by_actual() already does all the work,
doesn't it?
If i don't miss any details the following patch is enough:

diff --git a/usr/sbc.c b/usr/sbc.c
index 48dab04..f3248a1 100644
--- a/usr/sbc.c
+++ b/usr/sbc.c
@@ -230,6 +230,17 @@ static int sbc_rw(int host_no, struct scsi_cmd *cmd)

        uint16_t asc = ASC_LUN_NOT_SUPPORTED;
        struct scsi_lu *lu = cmd->dev;

+       switch (cmd->scb[0]) {
+       case READ_6:
+       case READ_10:
+       case READ_12:
+       case READ_16:
+               if (cmd->tl != scsi_get_in_length(cmd))
+                       scsi_set_in_resid_by_actual(cmd, cmd->tl);
+       default:
+               break;
+       }
+
        ret = device_reserved(cmd);
        if (ret)
                return SAM_STAT_RESERVATION_CONFLICT;
--
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